Inkjet printers are used to reproduce digital images on substrates by delivering variably sized droplets of fluid, such as inks. These fluids generally include a dye or pigment to form the desired color palette together with one or more solvents, whether aqueous or non-aqueous. In addition, they often include additional additives depending on desired properties. Among these include various surfactants, humectants, biocides, and dispersion aids.
Among the recent adaptations of inkjet printing is its use in the production of security documents, such as checks. To this end, fluids have been supplemented with various additives to provide magnetizable properties. Typically, these magnetizable fluids include iron oxide and are printed in special typefaces. The print is read by magnetizing the characters then passing them over a read head, which detects and interprets particular waveforms. This process is referred to as Magnetic Ink Character Recognition (MICR). Among the benefits of MICR is that it permits reliable reading of characters even when overprinted with stamps or other nonmagnetic inks. Thus, MICR provides an encouraging approach for securing documents.
The widespread adoption of MICR has led to increased demand for improved magnetizable fluids; however, there remain significant challenges in their development. Among these include challenges of increasing print speed, resolution and shelf life. For instance, large magnetizable particles tend to retain their imparted charge over longer lengths of time and thus have a longer shelf life compared to smaller particles; however, solutions containing large particles tend to settle, slow printing speeds and decrease resolution. Accordingly, there remains a need to develop new magnetizable fluids for use with inkjet printing that balance increased shelf life with increased print resolution and print speed.